10 Star Trek Moments More Important Than You Realised

One of the most interesting story arcs throughout Voyager was The Doctor's journey towards becoming sentient.

The Mark I Emergency Medical Holograms were a new Starfleet technology designed to help the medical staff aboard a ship, but when Voyager's entire medical staff was wiped out in the pilot, The Doctor was the only one trained in advanced medicine, and was forced to stay online much longer than his programmers intended. Because he was online for so long, he started forming complex relationships with the crew and expanding his own program to include knowledge on things he was interested in, like opera and writing.

At the beginning of Voyager he was treated like a simple machine by most of the crew, but they slowly accepted him as an individual.

When The Doctor's rights were called into legal question in the episode Author, Author, Janeway assembled the crew to defend him and prove that he is, in fact, self-aware. One of the most compelling arguments was that The Doctor had actually disobeyed orders in the past (in the episode Flesh And Blood). His programming explicitly prohibited this, which proved for a fact that he had become more than just a program; he could make decisions for himself.